All squamous cell carcinoma lesions are thought to begin via the repeated, uncontrolled division of cancer stem cells of epithelial lineage or characteristics. Accumulation of these cancer cells cause a microscopic focus of abnormal cells that are, at least initially, locally confined within the specific tissue in which the progenitor cell resided. This condition is called squamous cell carcinoma in situ, and it is diagnosed when the tumor has not yet penetrated the basement membrane or other delimiting structure to invade adjacent tissues. Once the lesion has grown and progressed to the point where it has breached, penetrated, and infiltrated adjacent structures, it is referred to as “invasive” squamous cell carcinoma. Once a carcinoma becomes invasive, it is able to spread to other organs and cause a metastasis or secondary tumor to form.
Oral cancer is a subtype of head and neck cancer and is any cancerous tissue growth located in the oral cavity. It may arise as a primary lesion originating in any of the oral tissues, by metastasis from a distant site of origin, or by extension from a neighboring anatomic structure, such as the nasal cavity. Oral cancers may originate in any of the tissues of the mouth, and may be of varied histologic types: teratoma, adenocarcinoma derived from a major or minor salivary gland, lymphoma from tonsillar or other lymphoid tissue, or melanoma from the pigment-producing cells of the oral mucosa. There are several types of oral cancers, but around 90% are squamous cell carcinomas, originating in the tissues that line the mouth and lips.
Oral squamous cell carcinoma (OSCC) is a global health problem afflicting close to 300,000 people each year. Despite significant advances in surgical procedures and treatment, the long-term prognosis for patients with OSCC remains poor, with a 5-year survival rate at approximately 50%, which is among the lowest for all major cancers. High mortality associated with OSCC is often attributed to advanced disease stage at diagnosis, underscoring the need for new diagnostic methods targeting early tumor progression and malignant transformations.